Tech Team - Ratchet Blocks

    Ratchet blocks...they don't just go click!


    • Hold sheets in your hands longer
    • Make trimming easier
    • Get greater control

    Ratchet blocks are becoming an essential part of any boat's equipment. But what is it that they actually do? And how does it contribute to your sailing?

    Ratchet sheaveA ratchet block has two essential elements: A sheave that can grip the rope, and a pawl which prevents the sheave turning in the direction of the load. In use, the block takes part of the load in the sheave's grip and leaves the rest in the user's hand. The amount of load the sailor holds depends on the size of the sheave and the wrap of the rope around it.

    The upshot of this is that the sailor gains two big advantages. Firstly, they can hold the sheet in their hand much longer, making constant trimming much easier; Secondly, they have much greater control over the rope and can ease in a controlled manner without getting pulled into the block!

    The characteristics of the sheave should be that it grips the rope when you want it to, allows controlled easing, and doesn't damage the rope. This last aspect is often forgotten as sailors love the positive hold and then wonders why they need to replace their sheet every other week!

    What about turning the ratchet off?

    In light airs, if there is not enough pressure to pull the sheet through the block, you might want to turn the ratchet off. This is usually straightforward, using a switch located somewhere on the block. However, as soon as there is sufficient pressure, the ratchet should be turned back on, otherwise small gusts may be expended, pulling rope through blocks rather than pulling the boat through the water faster.

    What about automatic ratchet blocks?

    ratchet_ratchamatic.jpgThis brings us rather neatly to the subject of automatic ratchets, or Ratchamatics as they are termed in Harken parlance.

    These blocks have a ratchet that prevents the sheave from turning in one direction when the rope has load in it, but allows the sheave to spin freely when the rope is unloaded. This means that the ratchet helps you hold the load when trimming but does not restrict free movement of the sheet when you want it to run. A perfect example of this is when gybing an asymmetric spinnaker, as soon as you pull the load on after tacking, the ratchet springs back into action.

    So why not use Ratchamatics for everything?

    It comes down to preference, Dr. Harken doesn't like a Ratchamatic on the Laser mainsheet because the sheet flies out so quickly, using a standard on/off ratchet gives a little drag and allows him to move arthritically across the boat in a controlled manner. The more youthful among us might use their athletic ability to move much faster and might prefer the Ratchamatic.

    But it's all sounding a bit racy so far…

    What else can we do with a ratchet block?

    • Mainsheet control
    • Jib furling

    Using a ratchet block in your mainsheet reduces the feeling that if you un-cleat the sheet you will get dragged through the blocks, it gives you control. This is at least as important to cruising sailors as it is to the racy folk.

    Using a ratchet block on your jib furling line makes unfurling the sail, especially to a reefed position, a much more controlled and pleasant experience (and frees up the winch that you might have used for the same purpose).

    So, that's what ratchet blocks give you - Control! Holding loads and easing them become much easier.

    The one thing it doesn't do is make it easier to pull in, except in as much as it reduces the energy expended holding the load after each pull.

    And how much more pro does it sound when the block clicks madly as you pull in?

    That's all for now…

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